Solar Variability and Climate Change over the Late Holocene. D. Rind NASA/GISS NOAA Program: Abrupt Change in a Warming World

Transcription

1 Solar Variability and Climate Change over the Late Holocene D. Rind NASA/GISS NOAA Program: Abrupt Change in a Warming World

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3 It looks like the solar minimum may have been in Aug other indicators of coronal brightness suggest the same thing-and so I think cycle 24 has started. Also we do have a decent amount of polar field strength-which is the seed magnetic flux for the cycle and if we were going into a Maunder Minimum we would not likely have polar fields -since they are a consequence of the dynamo that drives the cycle. {Judith Lean, personal communication}

4 Lean and Rind, GRL, 2009

5 Lean and Rind 2008

6 Lean and Rind 2008

7 Lean and Rind 2008

8 IPCC 2007

9 IPCC 2007 Model Simulations

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11 Mechanisms for Solar Influence on Tropospheric Temperatures Variations in total solar irradiance (TSI) Influence on subtropical surface temperatures (land and sea), with subsequent atmospheric dynamic and moisture effects; influence on Hadley circulation Impact of solar irradiance variations on ocean/atm dynamics ENSO NAM/NAO NADW Variations in solar UV affecting stratosphere and stratospheric ozone Impact of stratospheric changes on tropospheric dynamics Hadley circulation Planetary waves

12 TSI EFFECTS Rind et al, 2004 TSI=-0.2% Spec Irrad+ Ozone TSI+ Anthro trace gases+ aerosols Anthro trace gases+ aerosols Annual surf temp, minus present

13 Van Loon et al., 2007 January-February data Also: Geay et al. 2007: Moderate -to--large positive solar forcing increases E-W temp gradient in the Pacific (upwelling thermostat effect) leading to enhanced La Nina conditions. Solar Max - Min: ENSO EFFECT Rind et al., 2008-> SSTs max-min White et al., 1997

14 Rind et al., 2005 Ts Table 2. Change in AO-index (30-50 N minus N) and NAO during Dec-Feb EXPERIMENTS VARIABLE SSTS SPECIFIED SSTS SLP/ NAO SLP/ NAO AO (MB) MB MB AO (MB) Equilibrium Results (MB) (M) (M) (MB) (M) 2CO CO2 Strat H2O Strat % TSI Volc Sulf+Soot % TSI NO O3 LS MB 10 MB (M) T 68mb

15 Observed Solar Cycle -Ozone Response Modeled Rind et al., 2008

16 June-August Van Loon and Shea 1999 Observed Modeled Rind et al., 2008

17 Rind et al., 2008

18 Influence on monsoon precipitation Bhattacharyya and Narsimha, 2005) {from above} Kodera and Shiabata 2006 {from below} Meeh et al., 2003 Rind et al., 2008

19 Rind et al., 2008

20 Van Loon and Labitzke 1988

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22 Effect on planetary waves December-February Solar max-min with East QBO Solar max-min with West QBO Rind et al., 2008

23 The Near Future Lean and Rind 2009

24 Conclusions Solar variability has likely affected recent decadal temperature trends and will probably continue to do so for the next decade - the overall warming for the past century is almost certainly due to greenhouse gas emissions. Solar variability may have contributed to cooler conditions during the last 500 years, although the magnitude of its effect is highly uncertain. It s unclear how solar variability relates to ENSO variations. Solar variability may affect NAM/NAO phase and NADW production, although it s not obvious that it has any special influence compared to other climate forcings. Solar influence on the troposphere appears to be the result of both 1) top-down forcing from solar UV variability, stratospheric ozone changes, and stratospheric temperatures affecting tropospheric stability 2) bottom-up through TSI influence on the surface, perhaps especially in the subtropics These effects seem capable of influencing the Hadley circulation and tropical (monsoon) precipitation, as recorded in some modern and paleo-records. They may also affect planetary waves and extratropical winter phenomena, perhaps in association with the QBO, although this has yet to be proven. With current estimates of future climate forcing, solar variability may produce a period of little global temperature change during the time period, similar to what has been observed over the last 10 years.

25 v q = u v y + f 0 ρ 0 z ρ 0 N v Φ 2 z 2 terms: 1)change of eddy angular momentum transport with latitude 2)change of eddy heat transport with altitude MORE POLAR COOLING ->MORE NEGATIVE NAO

26 NAM/NAO Effect Table 1a. Annual temperature changes in the variable SST experiments. The experiments in which the temperature changes in the troposphere and stratosphere are of the same sign are shaded. Values in parenthesis refer to the latitudinal slices listed in the column heading. Significant results at the 95% confidence level are in bold italics. Experiment SURF MB Trop 68Mb 1.5 MB Strat (D-F N) (16N-16S) 2CO (3.4) (3) CO2 Strat (1.0) (1) H20 Strat (0.4) (0) % TSI (3.0) (4) Volc (-1.6) (2.3) Sulf+Soot (-1.6) (42) % TSI (-1.6) (0) No O3 LS (-1.2) (-12) Table 1b. As in Table 1a but for the specified SST experiments. Experiment SURF MB Trop 68MB 1.5 MB Strat (D-F N) (16N-16S) 2CO (-0.7) (-1.5) CO2 Strat (0.4) (1) H20 Strat (0.0) (-1) % TSI (0.0) (0) Volc (0.0) (2.2) Sulf+Soot (-0.2) (41) % TSI (0.8) (-1) No O3 LS (-0.6) (-11)

27 Rind et al., 2008